Method and apparatus for operating cascade systems with regeneration



April 21, 1936. J M- GAlNES, JR l 2,037,714

METHOD AND APPARATUS FOR OPERATING CASCADE SYSTEMS WITH REGENERATIONFiled March 13, 1935 5 Sheets-Sheet 1 ATTORNEYS April 21, 1936- J. M.GAlNEs, JR 2,037,714

METHOD AND APPARATUS FOR OPERATING CASCADE SYSTEMS WITH REGENERATIONFiled March 13, 1955 l 5 Sheets-Sheet 2v INVENTO mm my amfm ATToRNEYsApril 2l, 1936. 1 M GAMES, JR 2,037,714

METHOD AND APPARATUS FOR OPERATING OASOADEy SYSTEMS WITH REGENERATIONFiled March 1.3, 1935 3 Sheets-Sheet 5 ATTORNEYS Patented Apr. 2l, 1936IMETHOD AND APPARATUS FOR OPERAT- ING CASCADE ERATION SYSTEMS WITHREGEN- John M. Gaines, Jrf, Kenmore, N. Y., assignor, by mesneassignments, to Union Carbide and Carbon Corporation, a' corporation ofNew York Application Mal-c1113, 1935, Serial No. 10,793

20 Claims.

This invention relates to a method and apparatus for operating a cascadesystem with regeneration to effect the transfer of a precious volatileliquid which tends to gasify under the conditions of ordinary transfer;the cascade principle being employed to reduce vaporization. losses.More specifically, it relates to an advantageous method and apparatusfor rejecting heat from a cascade system when arranged for rapidlytransferring a liqueed gas or like volatile material from a region ofrelatively low pressure to a region of relatively high pressure.

The invention has for its object generally an improved method utilizingthe cascade principle for reducing loss of material in the gas phasewhen effecting the desired transfer, by which heat is controllablysupplied for accelerating the transfer in a manner that conserves therefrigerating effect of the material being transferred and by which therefrigerating effect conserved is used when rejecting heat from thecascade system t reduce the internal energy of the material transferredin. the gas phase to a relatively small value.

More specifically, it is an object of the invention to provide a cascadesystem with an improved arrangement of transfer vessels for transferringliquids having boiling points below 273 K., such as certain liquefiedhydrocarbon gases, liquid oxygen, liquid nitrogen and the like, fromrsgons of relatively low pressure to regions at higher pressure togetherwith a method and means for conserving the refrgerating effect ofmaterial discharged from a final transfer vessel, whereby suchrefrigeration is utilized for rejecting heat from material in the gasphase being transferred in the system.

Another object of the invention is to provide a method and means forutilizing in greater degree than heretofore the condensing capacity ofthe liquid passed through transfer vessels for the reduction of theinternal energy of the material being transferred in the gas phasewhereby heat in the gas phase is carried away from the system in amanner that conserves both internal energy and gas material.

Other objects of the invention Will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others, and theapparatus embodying features of construction, combinations of elementsand arrangement of parts which are adapted to effect such steps, all ascxemplied in the following detailed disclosure, and the scope of theinvention will be indicated in he claims.

For a fuller understanding of the nature and objects of the inventionreference should be had to the following detailed description taken inconture. I In the copending application, Serial No. 3,219,

nection with the accompanying drawings, in which:

Fig. 1 is a view partly in elevation and partly in section showing a,mixed cascade system, i. e., one having transfer vessels connectedpartly in series and partlyV in parallel to embody the cascadeprinciple, arranged for conserving the refrigerating effect of thematerial discharged and rejecting heat from gas material transferred inaccordance with the present invention;

Fig. 2 is a similar view of a modied form of apparatus according to theinvention wherein heat is rejected from material in the gas phasetransferred between other vessels of the system; and

Fig. 3 is a similar view of another modification oflapparatus accordingto the invention.

When transferring volatile liquids of low boiling point from regions ofrelatively low pressure to receiving vessels at higher pressure by asystem of transfer vessels employing the cascade principle as set forthin the co-pending application, Serial No. 752,993, filed in the name ofJ. J. Murphy, loss of material in the gas phase is reduced bytransferring a portion of the internal energy contained in the gas phaseremainder to liquid being transferred within the system. Since the gasremaining after the discharge of liquid from a final vessel is to berecondensed, it is advantageous that the internal energy of material inthe gas phase be either kept at a low value or brought to a low valuebefore the recondensation is effected.

In the copending application, Serial No. 3,249, filed in the name of G.H. Zenner, it is shown how thermal energy alone, by means of a socalledthermal leg, is applied to accelerate the discharge of liquid from thefinal vessel of a cascade system and to reduce the total internal energycontained in the gas remaining after discharge by rapidly heating asegregated portion in the thermal leg to a relatively high temperafiledin the name of L. I. Dana, there is sho-wn a method and means fortransferring a portion of the internal energy containedin the gas phasek thermal leg whereby the material in the gas phase is quickly 'heatedto a relatively high temperature so as to keep the total internal energycontained in it to a value that is low compared to the internal energythat it would contain at a lower temperature but equal to dischargepressure while at the same time maintaining substantially unimpairedrefrigerating capacity of the material of the liquid phase discharged.This is accomplished by providing a suitable.regener ator in operativeconjunction with the thermal leg, whereby advantage is taken of therefrigerating capacity of the total discharge for reducing the internalenergy ofthe materialin the gas phase to a. relatively low value. l

By such means, the conserved refrigeration of the liquid phase diichargeis transferred t'o the gas phase already discharged from the cascadesystem, and the desired reduction of the internal energy of the gas tobe recondensed is accomplished. This reduction, however, has acumulative effect on succeeding charges'passed through the cascadesystem until a balance is reached. This cumulative effect followsbecause the gas which is passed into and condensed in the nextsucceeding charge of liquid carries less internal energy by an amountequivalent to the heat transferred to the heat storage and exchangingdevice. Therefore the second charge of liquid is not heated to as high atemperature as the previous charge and cools the exchanging device to alower temperature than the temperature' level imparted to it by theprevious charge.

The gas phase remainder of succeeding charges is therefore moreeffectively cooled to lower temparatures which in turn tends to preservethe refrigerating capacity of the material in the liquid phase at stilllower temperatures. The cumulative effect grows smaller with each cycleuntil a balanced condition is reached. Under certain conditionsliquefaction of some-of the gas which is cooled in the exchanging devicemay occur, depending upon the temperature and pressures involved.

The present arrangement applied to the improved cascade system effects areduction of the blow'down loss to a very small amount, since therefrigerating capacity of the material that may be under a pressure wellabove its critical pressure is used for reduction of the internal energyof the gas recycled for condensation in liquid. For a predeterminedcommercially allowable blowdown loss fewer steps of cascade equalizationneed be provided which results in a simplification of apparatus and areduction in the total weight of the system which is desirable when theapparatus is mounted on rolling stock for servicing storage andconsuming devices located at points distant from a centrally locatedliquefied gas production or storage plant.

Referring now to the drawings, and particularly to Fig. 1, there isshown a cascade system having four transfer vessels connected asparallel groups of two which are in series, so that the discharge ofsuccessive charges of the volatile material takes place alternately fromthe final vessel of each series. As illustrated, the parallel groupseach comprise a low pressure initial transfer vessel shown at I3 and I0.The low pressure vessels each have a liquid inlet connection shown at IIand II', a gas phase discharge connection shown at I2 and I2', and aliquid phase discharge connection shown at I3 and I3. The latter arearranged for transferring the liquid material into final vessels I5 andI5 which are disposed in succession below the initial transfer vessels;gas phase displacement connections I4 and I4 being arranged to leadrespectively from each final vessel to the corresponding inltial vesselfor controlling the transfer., The vessels I5 and I5 are preferablyprovided with liquid holding linings or baskets" spaced from the heavypressure resistant 4walls whereby heat contained in or passing throughthe walls is substantially excluded and the liquid protected. Leadingfrom the bottom of vessels I5 and I5' are connections I6 and I6 whichlead to the common connection I1 communicating with one pass of laregenerator shown generally at 20. This pass leads to the liquidreceiving and vaporizing device I8 which discharges gas at high pressureto consuming Adevices through the service connection I9.

The regenerator 20 is shown as of the separatepass type having passages2I and 23 separated by a heat storage wall 22. Passage 2I has its inletcommunicating with the connection I1 and its outlet connected to thedevice I8. The second passage 23 has its inlet 24 communicating with aconnection 25 that leads from the gas space of the vessel I5 and asimilar connection 25' leading from the gas space of vessel I5'; theseconnections being controlled by valves 25a and 25h, respectively. Theoutlet of passage 23 has a common communication with the connections 26and 26 which lead respectively to the gas distributing devices 21 and 21disposed respectively in the vessels I5 and I5'. Suitable means, forexample, check valves, as shown at 28 and 28', are preferably disposedin each of the connections 26 and 26 for preventing gas pressures invessels I5 and I5 from forcing the flow of liquid through theconnections 26 and 26 into the passage 23.

While the regenerator, shown diagrammatically at 20, is illustrated ashaving two passages separated by a heavy wall of heat storage material,it is contemplated that in actual practice the regenerator may have anysuitable form known to the prior art adapted for heat exchange in themanner desired between fluids of the character here transferred. Anadvantageous form of regenerator, adapted for use when liquid oxygen isto be transferred, comprises a bundle of relatively small bore heavyWalled copper tubes joined at each end to headers for the liquid phasedischarge pass, and a jacket surrounding the'bundle to provide a passfor the gas to be cooled. Provision'is also made in the construction fortemperature and pressure effects and for efficient heat exchange as wellas the presence of the desired amount of metal in the tubing walls forthe storage and exchange of heat, in the manner here set forth, betweenpredetermined temperature levels. A detailed showing of such form is,however, omitted in the interest of clearness of illustration in thedrawings, the form of the regenerator here employed being no part of theinvention.

Means are also provided for effecting cross equalization between vesselsIIJ and I in the form of a conduit 29, controlled by valve 30,connecting distributors 3I and 3I; similar means being provided foreffecting equalizations between vessels I and I0 and between vessels I5and I0 in the form of conduits 32 and 32 which connect distributors SIand 3 I with the upper portions of vessels I5 and I5', respectively.

A common thermal leg is provided, as shown at 33, for accelerating thedischarge from vessels I5 and I5. This leg is connected in such manneras to heat a Withdrawn portion of the charge Without heating the majorportion that is discharged, and comprises lower and upper headersconnected by a plurality of tubular conduits of heat conductingmaterial, the whole being exposed to the action of a suitable heatingmedium, for example, steam.

In such arrangement, the lower header ls connected with the lowerportions of vessels I5 and I 5 by connections 34 and 34 while the upperheader is connected to the upperjportions of the vessels by conduits 35and 35', respectively..

Each of the conduits or connections is controlled by valves interposedtherein as follows: Conduits II, I2, I3, I4, I6, 25, 32, 34 and 35 arecontrolled by valves IIa,-I2a, I3a, I4a, IIia, 25a, 32a, 34a and 35a,respectively, while conduits II I2', I3', I4', I6', 25', 32', 34' and35' are controlled by valves IIb, I2b, I3b, I4b, I6b, 25h, 32h, 34h and35h, respectively.

In the operation of this four vessel system, the

passage of liquid and gas through the passes 2| and 23 is more or lesscontinuous by virtue of the alternate discharge of vessels I5 and I5 andin consequence the heat transfer surfaces are einciently used. Assumingthat vessel I5 has just been lled with liquid and that vessel I5' isfull of gas (which may be termed hot gas by reason of its relativelyhigh temperature with reference to the liquid, although in the case ofliquid oxygen, the gas temperature may be in the neighborhood ofatmospheric temperature), discharge of liquid is elected through theconnection I6 only after an equalization of pressures between thevessels I5' and I5 is accomplished. To this end valves 25h and 28 arerst opened in their respective connections 25' and 26 and gas passedthrough the pass 23 to flow from vessel I5 to I5 where its heat istransferred to and stored in the wall 22. When equalization issubstantially completed, valves 25h and 28 are closed and liquidwithdrawal from vessel I5 through the connection I6 is initiated whenthe thermal leg 33 is opened to communication with vessel I 5. To thisend, valves 34a and 35a are opened, and gas material is circulatedthrough thermal leg 33 where it becomes heated to a relatively hightemperature, whereby pressure is rapidly built, so that when valve I 6ais open the relatively cold gas material in vessel I5 is dischargedthrough passage 2| of the regenerator 20 and through heating device I8to receiving devices coupled to the line I9 at e. It is seen thatpractically all of the material discharged is at a low temperature sincethe major portion of the heat introduced by the thermal leg will remainin the gas left in vessel I5 after discharge.

'I'his gas phase remainder is first cooled by the regenerator 20 whenvessel I5 and vessel I5 containing a new charge of liquid are pressureequalized. In accordance with the cascade principle, the remainder,after the cross equalization, is conducted into a charge of liquid invessel I by opening valve 32a for a second step of equalization withfurther condensation. A third step of equalization is practised by crossequalizing between vessels I0 and I0' by opening valve 30 after theliquid charge of vessel I0 has been transferred to vessel I and vesselI0' lled with a new charge of liquid from the supply source, suchtransfer being preceded by a transfer of residual gas to vessel I0 asWell as liquid from vessel III to vessel I5.

In Fig. 2 is shown another four vessel system 'which conducts to heaterIIB.

in which the gas conducted into a succeeding charge for condensation ina vessel in series relation with one iinal vessel is cooled bycountercurrent flow in heat exchanging relation with materialA beingdischarged from the other nal vessel.

The transfer vessels here are of similar construction to those shown inFig. 1 and are similarly connected, equivalent parts being designated bythe same numerals. Cross equalizing connections, however, are omitted inthe interests of clearness of illustration in the drawings. Material ofthe liquid phase discharged from the nal vessel I5 through dischargeconduit II6 is caused to pass through one pass of countercurrentregenerator or heat exchanger 40 whose warm end is connected to commonconduit III'I From thegas space of vessel I5 aconduit 4I conducts gas tobe cooled to the warm end of the return pass of a similar regenerator orheat exchanger 40 from the cold end of which the gas is conducted to thedistributor 3I in vessel IIJ by conduit 42. Similar conduits areprovided for the discharges from vessel I5', conduit I I6' conductingfrom the liquid phase to exchanger 40 while conduit 4I conducts from thegas phase to exchanger 40'. Valves for controlling the respectiveconduits are provided at II6a, II6b, 4Ia, and 4Ib.

If desired, a single countercurrent heat exchanger may be providedinstead of the two individual exchangers. This is readily accomplishedby suitable arrangement of the connections and the control Valves.

'I'he heat exchangers in this form of the invention need not be providedwith any substantial amount of heat storage material since the flow ofthe two fluids between which heat is exchanged occurs substantiallysimultaneously. Thus when vessel I5 is being discharged of materia1 inthe uquid phase through conduit Iis and one pass of exchanger 40', gasis at the same time discharged from vessel I5' through conduit 4I', theother pass of heat exchanger 4D and conduit 42 to vessel IIJ'. The ow ofgas may be regulated by the adjustment of the control valve 4Ib so as tooccur during the entire time of. discharge from vessel I5. It will beseen that the residual gas in vessel I5' after the displacement of thecharge is conducted into the initial vessel I Il and during its passagethe gas is cooled by heat exchange in countercurrent ow with the liquidwhich is being discharged,

substantially simultaneously from the vessel I5. When the pressures areequalized, the augmented charge of liquid in vessel IU is transferred tovessel I5 by opening valves I3b and I4b for the required period, afterwhich vessel I0' is vented in preparation for refilling. Crossequalizations between vessels l0 and I0' and vessels I5 and I5' aredispensed with but may be practised if desired.

In the arrangement of the apparatus shown in Fig. 3, advantage is takenof the mass of the metal in the pressure retaining walls of the finalvessels to provide the desired heat storage capacity. Here the nalvessels of the transfer system, shown at 45 and 45', are of similarconstruction to vessels I5 and I5 and have heavy metal pressureresistant walls and baskets for holding liquid thermally insulated fromthe walls. The vessels 45 and 45'- are connected with individual thermallegs 46 and 46 although they may be connected to a common thermal leg bysuitable connections similarly to the arrangement shown in Figs. 1 and2. Where individual thermal legs are provided as shown the control valvewith its attendant restriction to gas flow may be and is omitted fromthe connec` tions 41 and 4l connecting the thermal legs to the gas spaceof vessels 45 and 45. Communication of the thermal legs with the liquidspace of vessels 45 and 45 is had through connections 48 and 48 when therespective control valves 48a and 48h are open.

Refrigeration is transferred to the Walls of vessels 45 and 45 bycoiling extended portions of the discharge conduits 49 and 49 disposedaround the vessels and in thermal contact With the outer surface of thewalls. Conduits 49 and 49 lead from conduits 48 and 48' and connect to acommon heating coil or heater 50 Whichhas a portion l leading to thereceiving devices that are coupled at e.

Equalizing connections are provided as follows: at points 52 and 52after the conduits 49 and 49 leave Contact with the walls of theirrespective vessels, cross branch couplings are provided. One branch ofcoupling 52 is connected with a distributor 53' in vessel 45 byconnection 54 and similarly one branch of coupling 52 is connected withdistributor 53 within vessel 45 by connection 54. The other branches ofcouplings 52vand 52 are connected by' conduits 55 and 55 to distributors3l and 3l' in vessels i0 and I0. Control valves 49a and 49h are providedin conduits 49 and 49 in the portions between couplings 52, 52 and thejunction with heater 50. Control valves 54a, 54h, 55a and 55h are alsoprovided in conduits 54, 54', 55 and 55 respectively.

In this form the discharge from the liquid phase of the final vesselsand the outflow of gas when equalizing pressures between vessels bothoccur through the same conduits 49 or 49. It is contemplated, however,that it may be desirable to provide a separate conduit also coiled inthermal contact with the vessel walls for conducting the gas to becooled when equalizing pressures.

The operation of this latter form of apparatus takes place as asubstantially continuously repeated cycle of events involving thealternate filling of the initial vessels with liquid to be transferred.As a convenient starting point in describing the sequence of events inthe cycle, it will be assumed that vessels 45 and I0' have been filledwith chargesof liquid. Thermal leg 45 is set in operation by openingvalve 48a which produces a rapid building of pressure due to theunrestricted flow of the gas vaporized in the thermal leg throughconduit 41 into Vessel 45. The pressure, which soon exceeds that of thereceiving devices, forces the major portion of the volatile material outthrough conduit 49 into the receiving devices including heater 55 whenthe valve 49a is open. The conserved refrigerating capacity of thematerial so discharged causes a removal of heat from the metal of thewalls of vessel-45.

During discharge, gas and liquid are exchanged between vessels i6 and 45aft-er pressures are equalizcd between them. The pressure equalizationis accomplished by opening valve 5519 so that iiow of gas occurs fromvessel 45', through conduits 49 and 55 to distributor 3|' and thereforethe gas of the second step of equalization is also cooled by a storedrefrigerating effect in the shell of vessel 45. After the equalization,valves I3b and I4b are opened to drop the liquid charge from vessel l0'into the basket in vessel 45', at the same time transferring gas fromvessel 45 to vessel I0.

When vessel 45 is discharged and vessel 45' is charged, all valves areclosed and the first step of cascade condensation is initiated byopening valve 54a. The gas phase remainder in vessel 45 having arelatively high temperature and pressure flows through conduits 49 and54 to distributor 53' disposed in the liquid in vessel 45'. This gasduring flow through conduit 49 transfers heat to the metal of the wallsof vessel 45 thereby losing a substantial amount of internal energybefore it is passed in contact with the charge in vessel 45. The chargein vessel 45 condenses a larger portion of the gas and is heated to asmaller degree than if regeneration had not been practised. Therefore,the liquid charge after the equalization is a better refrigerating agentfor cooling the heat storing material.

After the cross equalization, the second equalization, using theremainder of the Warm gas in Vessel 45, is practised by closing valve54a and opening valve 55a. The gas in consequence fiows, after heatexchange with the heat storing material, through conduit 55 todistributor 3l so that a large portion of it is condensed in the chargeof volatile material in vessel I0.

By the methods and apparatus of the present invention, it is seen thatthe gas material transferred is self-compressed with a high degree ofefficiency and economy. This is accomplished by the several methods ofpreserving the refrigerating capacity of the liquid charges and theefficient utilization of the refrigerating capacity for the reduction ofthe blow-down loss to commercially immaterial amounts.

The refrigerating capacity of the liquid charges is preserved byexcluding heat therefrom by suitable means; for example, by insulatingthe charge from the heat of the Walls of the transfer vessels by meansof linings or baskets disposed interiorly and/or insulating jacketsdisposed exteriorly. Also, it is seen that by discharging the finalvessels to the receiving devices by heating only a portion of the chargein a thermal leg, much heat is excluded; also, by precooling the gaswhich is to be condensed during either or both first and subsequentsteps of pressure equalization, theinternal energy of the gas materialbeing transferred is kept at a low value.

The refrigerating capacity of the liquid charges is used first withinthe cascade system for recondensing the gaseous remainder in the finalvessel after a discharge from the liquid phase and secondly forrejecting heat from the system by precooling the gas material beyond thefinal discharge vessel so as to carry away some of the heat otherwisecontained in the gaseous material passing backwardly through the system.

Since certain changes in carrying out the above process and in theconstructions set forth, which embody the invention may be made Withoutdeparting from its scopeit is intended that all matter contained in theabove description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

Having described my invention, what I claim as new and desire to secureby Letters Patent is:

1. A method of transferring a volatile liquid material that evolves agas phase on accountvof heat added during the transfer from a region ofrelativelylow pressure to a region of relatively` high pressure, whichcomprises causing the passage of said material in a succession ofmetered charges in countercurrent relation to the gas phase-throughs)succession of steps of increased pressures.- excluding substantially allheat of external origin from said material prior to the passing of apredetermined point, controllably vpredetermined point while maintainingpressure heating to a relatively high temperature a portion of eachcharge withdrawn after passage of said equilibrium between the chargeand the withdrawn portion whereby the pressure acting on the charge andthe 4volume of the charge are raised to relatively high values withoutsubstantial impairment of the refrigerating capacity of said charge,flowing by the agency of increased pressure and volume the charge tosaid region oi relatively high pressure, absorbing and storingrefrigeration from the material flowed, utilizing the storedrefrigeration for cooling after said flow the portions ofmaterial in thegas phase which were heated to relatively high temperature, and passingthe material in the gas phase in countercurrent heat exchanging relationwithf the material being advanced through steps of increased pressuresprior to the passage of said predetermined point.

2. A method of transferring a volatile liquid material that evolves agas phase on account of heat added during the transfer from a region ofrelatively low pressure to a region of relatively high pressure, which'comprises causing the passage of said material in a succession ofmetered charges in countercurrent relation to the gas phase through asuccession of steps of increased pressures, excluding substantially allheat of. external origin from said material prior to the passing of apredetermined point, controllably heating to a relatively hightemperature a portion of each charge withdrawn after passage of saidpredetermined point while maintaining pressure equilibrium between thecharge and the withdrawn portion whereby `the pressure acting on thecharge and the volume of the charge are raised to relatively high valueswithout substantial impairment of the refrigerating capacity of saidcharge, flowing by the agency of increased pressure and volume thecharge to said region of relatively high pressure, utilizingrefrigerating capacity of `the material flowed for cooling material inthe gas phase which is passed countercurrent to and in heat exchangingrelation with the liquid being advanced through said steps of increasedpres-v sures whereby so large a portion of the gas is condensed thatthe-ultimate loss of material in the gas phase is reduced to animmaterial amount.

3. Amethod of supplying gas material to a receiving vessel at apredetermined superatmospheric pressure which comprises isolating ametered charge of liquefied gas in one of a plurality of transfervessels into which it has been introduced at a pressure less than saidpredetermined pressure, raising the pressure environment of said chargeto a value exceeding said predetermined pressure and simultaneouslyincreasing the volume by separately heating a portion of said chargewhile in substantial pressure equilibrium with said charge Withoutsubstantially impairing the refrigerating capacity of the portion notheated, discharging the portion of said charge not heated to saidreceiving vessel leaving a heated gas phase remainder in said transfervessel having a pressure equal to said predetermined pressure,indirectly utilizing the refrigergas introduced atv alpressure less thansaidprede` termined pressure in a secondtransfer vessel vwhere it'ismaintained substantially insulated' against mnow of heat for a' `desiredperiod of time,

and conducting a cooled portionof said remainder into said second chargewhereby'a substantial portion is condensed in and'augments said secondcharge.

4. A method of transferring volatile material that has a gas phaseevolved due to heat gained in the transfer from one vessel to another incascade relation, which method comprises introducing a meteredcharge ofmaterial in the liquid phase into one vessel while another vesselcontains material in the gas phase at a relatively high pressure,equalizing the pressures between said vessels while effectingcondensation of gas material drawn from the high pressure vessel andpassed into the low pressure vessel, interchanging under the inuence ofgravity the liquid and gas phases between said vessels, controllablyheating a portion of the charge of liquid in said high pressure vesselto increase the pressure and volume of the charge to values sufficientto enable said charge to enter the receiver while preserving therefrigeration capacity oi the major portion of said charg-e, flowingsaid major portion to said receiver, and during said ilovr extractingand utilizing said refrigerating capacity for cooling gas transferredbetween vessels when effecting said equalization to aid ,thecondensa-tion.

5. A method of operating a volatile liquid transfer system havingtransfer vessels arranged in cascade, which comprises conserving therefrigerating capacity of a charge of volatile liquid when passed into anal transfer vessel by excluding substantially all heat inflow from thewalls of said vessel, controllably heating to a relatively hightemperature a sufcient portion of said charge for increasing thepressure and volume sufficiently toy displace the balance from saidfinal vessel at a desired pressure Without substantially increasing thesensible heat of said balance, transferring a refrigerating effect fromsaid balance being displaced from said nal vessel to a heat storingmaterial Where it is held for a desired period of time, and bringinginto thermal contact with said heat storing material gas remaining insaid nal vessel after displacement of the balance when said gas is beingpassed to other vessels of the system.

6. A method of operating a volatile liquid transfer system havingtransferA vessels arranged in cascade, which comprises conserving therefrigerating capacity of a charge of volatile liquid when passed into afinal transfer vessel by excluding substantially all heat inowfrom theWalls of said vessel, controllably heating to a relatively hightemperature a sufficient portion of said charge for displacing thebalance from said nal vessel at a desired increased pressure and volumeWithout substantially increasing the sensible heat of said balance, andutilizing the refrigerating capacity of said balance for cooling cludingsubstantially all heat inflow from the walls of said vessel,controllably heating to a relatively highv temperature asufncient'portion of said charge for increasing the pressure and volumesuillciently to displace the balance from said final vessel against apredetermined pressure without substantially increasing the sensibleheat of said balance, storing a refrigerating effect obtained from saidbalance during the displacement of said balance, and transferring saidrefrigerating effect to gas passed-from a vessel atV high pressure to avessel at lower pressure in the system.

8. A method of operating a volatile liquid transfer system havingtransfer vessels arranged in cascade which comprises, conserving therefrigerating capacity of a charge of volatile liquid when passed into afinal transfer vessel by excluding substantially all heat inflow fromthe walls of said vessel, controllably heating to a relatively hightemperature a sumcient portion of said charge for increasing thepressure and volume suillciently to displace the balance from said nnalvessel against a predetermined pressure without substantially increasingthe sensible heat of said balance, transferring a refrigerating effectfrom said balance being displaced from said final vessel to gas beingpassed from another nal vessel to a vessel containing a charge of liquidat a lower pressure.

9. In a method of transferring charges of volatile liquid material froma source at low pressure to a receiver at relatively high pressure bymeans of transfer vessels connected in cascade relation and having finaltransfer vessels arranged in parallel, the step which comprises coolinggas being passed from one nal vessel at a relatively high temperatureand pressure into thermal contact with a succeeding charge for partialcondensation by passing said gas in simultaneous heat exchangingrelation with the volatile material being discharged from another finaltransfer vessel to the receiver.

10. In a method of transferring charges of volatile liquid material froma source at low pressure to a receiver at relatively high pressure bymeans of transfer vessels connected in cas- -cade relation and havingnal transfer vessels arranged in parallel, the step which comprisescooling gas being passed from a ilnal vessel at a relatively hightemperature and pressure into admxture with a succeeding charge at alower pressure and temperature for partial condensation, by flowing saidgas countercurrent to and in simultaneous heat exchanging relation withthe volatile material being discharged from another flnal transfervessel to the receiver.

l1. In. a cascade system for transferring volatile liquid material froma low pressure supply source to a receiver at higher pressure, thecombination with a plurality of transfer vessels for holding charges ofvolatile liquid at successively higher pressures, of means forprotecting said charges from the influence of heat of external origin,means for heating a portion of the charge in a final transfer vessel atthe highest pressure to a relatively high temperature while maintainingthe refrigerating capacity of the balance of the charge in the vesselrelatively unchanged,

means for conducting said balance to said re' ceiver, means associatedwith said conducting means for transferring a refrigerating effect fromsaid balance to gas of relatively high temperature discharged from afinal vessel of the system, and means for passing said gas in heatexchanging relation with charges of volatile liquid at successivelylower pressures.

l2. In a cascade system for transferring volatile liquid material from alow pressure supply source to a receiver at higher pressure, thecombination with a plurality of transfer vessels for holding charges ofvolatile liquid at successively higher pressures, of means forprotecting said charges from the influence of heat of external origin,means for heating a portion of the charge in a final transfer vessel atthe highest pressure to a relatively high temperature while maintainingthe refrigerating capacity of the balance of the charge in the vesselrelatively unchanged, means for conducting material of the liquid phasein heat exchanging relation with a heat storing material from a finalvessel to said receiver, and means for passing gas from a final vesselin heat exchanging relation first with said heat storing material andthen with charges of volatile liquid in other transfer vessels at lowerpressures.

13. In a cascade system for transferring volatile liquid material from alow pressure supply source to a receiver at higher pressure, thecombination with aplurality of transfer vessels for holding charges ofvolatile liquid at successively higher pressures, of means forprotecting said charges from the influence of heat of external origin,means for heating a portion of the charge in a nal transfer vessel atthe highest pressure to a relatively high temperature to increase thepressure and volume while maintaining the refrigerating capacity of thebalance of the charge in the vessel relatively unchanged, means forconducting material of the liquid phase in heat exchanging relation witha heat storing material from a final vessel to said receiver, and meansfor passing gas in heat exchanging relation with said heat storingmaterial from a flnal vessel to another vessel of the system whichcontains a charge of liquid at lower pressure.

A14. In a cascade system for transferring volatile liquid material froma low pressure supply source to a receiver at higher pressure, thecombination with a plurality of transfer vessels for holding charges ofvolatile liquid at successively higher pressures, of means forprotectingsaid charges from the influence of heat of external origin, means forheating a portion of the charge in a nal transfer vessel at the highestpressure to a relatively high temperature to increase the pressure andvolume while maintaining the refrigerating capacity of the balance ofthe charge in the vessel relatively unchanged, said final vessel havinga heavy metal pressure retaining wall and a lining means for holding thecharge of volatile liquid in relatively poor thermal contact with saidwall, means for conducting material of the liquid phase discharged froma final transfer vessel in heat exchanging relation with said pressureretaining wall to said receiver, and means for passing gas from a naltransfer vessel in heat exchanging relation first with said cooledpressure retaining wall and then with charges of volatile liquid inother transfer vessels at lower pres- .Suresphases in heat exchangingrelation, of means for discharging material from the liquid phase of afinal transfer vessel by heating a suflicient portion of the volatilematerial in the vessel to a relatively high temperature for increasingthe pressure and volume to desired values suiiicient to insure expulsionwithout impairing the refrigerating capacity of the material which isdischarged, and means for applying said refrigerating capacity forprecooling material in the gas phase during said countercurrent passage.

16. In a cascade system for transferring a volatile liquid material froma supply vessel where it is held at a relatively low pressure to areceiver under a relatively high pressure, the combination with aplurality of Jtransfer vessels adapted for holding a succession vofcharges of material in liquid phase and material in the gas phaseevolved due to heat gained in the transfer and for effecting thecountercurrent passage of liquid and gas phases in heat exchangingrelation, of means for discharging material from the liquid phase of anal transfer vessel by heating a suflicient portion of the volatilematerial in the vessel to a relatively high temperature for increasingthe pressure and volume to desired values without impairing therefrigerating capacity of the' material which is discharged, and a heatstorage and exchanging device having a pass for volatile material whichis discharged from the liquid phase of a final transfer vessel and apass through which ows material in the gas phase during saidcountercurrent passage.

17. In a cascade system fortransferring a volatile liquid material froma supply vessel where it is held at a relatively low pressure to areceiver under a relatively high pressure, the combination with a pairof transfer vessels connected. in series the rst discharging into thesecond for holding charges of said material and gas evolved therefromdue to heat gained on discharge from the second of said vessels, ofmeans associated with the second of said vessels for preserving therefrigeration of said charges of material in the liquid phase fromimpairment by inflow of undesired heat, means for equalizlng thepressure of said rst and second vessels by'conducting gas from saidsecond vessel in intimate contact with liquid in said iirst vesselwhereby a desired portion of gas is Acondensed by the refrigeration .ofthe liquid, means for causing an interchange of gas and liquid betweensaid vessels, a thermal leg for increasing the pressure and volume ofsaid liquid in said second vessel to values sufficient for eecting adischarge to said receiver without impairing the refrigerating capacityof the material discharged, means for taking up and ten'iporarilyvstoring a refrigerating effect from said material as discharged, andmeans for transferring said refrigerating effect to gas being conductedfrom said second vessel to said rst vessel.

18. In a cascade system for transferring volatile liquid material from asupply vessel where it is heldV at relatively low pressure to a receiverunder a relatively high pressure, the combination with a plurality oftransfer vessels interposed between the supply vessel and receiverarranged as two parallel groups each consisting of a'low pressure vesseland a high pressure vessel in series disposed to pass a succession ofcharges of said material; of means associated with said vessels forprotecting said charges from the iniiuence of heat of external origin,means associated exclusively with said high pressure vessels for heatinga portion of the charge contained therein to a relatively hightemperature While maintaining the refrigerating capacity of the lbalanceof said charge relatively un` changed, withdrawal means arranged forconducting said balance to the receiver, passage means connected to saidhigh pressure vessels for conveying gas collected therein at highpressure to a region of lower pressure and temperature where, by partialcondensation, a portion of the gas is converted into liquid, and meansassociated with said withdrawal means and said passage means for causingthe gas being conveyed to a region of low pressure to pass incountercurrent heat exchanging relation with the liquid being passed tosaid receiver.

19. In a cascade system for transferring volatile liquid material from asupply vessel where it is held at relatively low pressure to a receiverunder a relatively high pressure, .the combination with a plurality oftransfer vessels interposed between the supply vessel and receiverarranged as two parallel groups each consisting of a low pressure vesseland a high pressure vessel in series disposed to pass a successionofcharges of said material, of means associated with said vessels forprotecting said charges from the influence of heat of external origin,means associated exclusively with said high pressure vessels for heatinga portion of the charge in a high pressure vessel to a relatively hightemperature, withdrawal conduits leading from each of said high pressurevessels having a common manifold leading to the receiver, equalizationpassages leading from the gas space of each of said high pressurevessels to the liquid space of another vessel whereby when at lowerpressure a passage of gas into liquid takes place producing partialconversion by condensation of the gas into liquid, and a two-pass heatexchanging device associated with each withdrawal conduit, one pass ofeach device being interposed in the withdrawal conduit while its otherpass is interposed in the equalization passage leading from the otherhigh pressure vessel.

20. In a cascade system for transferring'volatile liquid material from asupply vessel where it is held at relatively low pressure to a receiverunder a relatively high pressure, the combination with a pluralityoftransfer vessels interposed between the supply vessel and receiverarranged as two parallel groups each consisting of a low pressure vesseland a high pressure vessel in series disposed to pass a succession ofcharges of said material, of means associated with said vessels forprotecting said charges from the influence of heat of external origin,means associated exclusively with said high pressure vessels for heatinga portion of the charge in a high pressure vessel to a relatively hightemperature, withdrawal conduits leading from each of said high pressurevessels and having a commonl manifold leading to the receiver,equalization passages leading from the gas space of each of said highpressure vessels and discharging into the liquid space of the lowpressure vessel of. the series, and a two-pass 'neat exchangerassociated with each withdrawal conduit, each of which has one passinterposed in its associated withdrawal conduit and the other pass incommunication with the equalization passage leading from the other ofsaid high pressure vessels; the communication to said passes beingarranged to effect the countercurrent passage of the gas and liquid insaid heat exchangers.

JOHN M. GAINES. Jn.

